ALL-ELECTRIC HVAC EFFICIENCY:

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1 Fall 2017 A Thermo King publication for the mobile climate control industry ALL-ELECTRIC HVAC EFFICIENCY: TRUTH AND FACT VS. UNSUBSTANTIATED CLAIMS The term efficiency has been applied very broadly when it comes to all-electric HVAC, specifically on new battery buses. In layman s terms, efficiency can be defined as the amount of power being input (in kilowatts []) versus the amount of power being used to achieve a defined output in Kw. If the output of the HVAC system needs to be 18, how many is required to achieve that output? The method that requires the least input to get the desired output is the most efficient. This article will try to define efficiency within several contexts in which the term is used. Here are a few scenarios to consider: CONTINUED ON PAGE 2

2 ALL-ELECTRIC HVAC EFFICIENCY...CONTINUED FROM PAGE 1 Performance Specifications: Customers continue to ask for specific pull down performance (like Houston and White Book tests) when they write specifications for all-electric HVAC systems. Take a look at the pulldown chart above and assume that these are three different HVAC systems. Is the system that pulls down the fastest the most efficient? The answer is yes, if the goal is achieving air conditioning efficiency with a pre-determined temperature in a predetermined amount of time with no regard for the power required. Power Consumption: What if you changed the parameters of the pull down and took time out of the equation? Would you then only look at the power consumption required for pull down to a predetermined temperature? The bar graph shows three different results for power consumption during the same pulldown. Is the system that uses the least amount of power the most efficient? The answer is yes if power conservation and power management are your pre-determined objectives. This is a critical parameter for electric efficiency. Cabin Temperature Maintenance: This is also a requirement in the performance specifications. Users typically want the cabin temperature to be maintained between 68 and 72 degrees Fahrenheit on a fully-loaded bus with normal door openings. If two different systems were tested, and one could achieve these results using 30% less energy, which one is the most efficient? The answer is obvious in this case. Unsubstantiated Claims: These three scenarios clearly illustrate the ambiguity that can be associated with making broad claims of better efficiency. We advise you to question any claims of improved efficiency without comparative data. This data should represent actual testing, under the same conditions, for the same amount of cooling. The integrity of the data is best when it comes directly from fleets. All of Thermo King s all-electric HVAC systems use R407C, the most efficient refrigerant for large bus HVAC. It has been demonstrated in actual fleet operations that R407C provides an 8% reduction in energy consumption for the same amount of cooling. This is not an unsubstantiated claim! Conclusion: These efficiency claims surfaced with the coming of the battery bus, where efficiency is defined by the range of the bus. Customers should be reminded that we are still early in this journey, and that the sacrifices for extended range have not been clearly defined. For example, you can shut off the HVAC all together and get miles in additional range from the battery. While that is not feasible, it is the responsibility of all HVAC suppliers to show the kilowatt per hour energy consumption under several specific conditions like ambient temperature and desired interior temperature to start with. As with previous new technologies, the gains from other operational efficiencies will become apparent as the buses are operated in actual transit duty. 2 Get Comfortable

3 ALL-ELECTRIC HVAC HEAT PUMPS ARE THEY RIGHT FOR YOUR OPERATION? A PRELIMINARY FEASIBILITY ANALYSIS For the last twenty years, users have been asking HVAC suppliers for heat pumps. These requests came mainly from users in moderate climates who were familiar with the use of heat pumps in their home HVAC systems. Needless to say, it was easy to talk the requester out of it in a diesel engine market where heat was free. Today, with the introduction of battery bus Ambient technology, where Temp F heat can require as much as twice the energy needed for air conditioning, the heat pump conversation becomes relevant. The theory is that the heat pump would reduce the amount of power taken from the battery if it replaced electric resistance heaters, thereby increasing the Kilowatt hours of the battery and extending the range of the bus. While the theory is sound, and when in use the heat pump is more efficient, the heat pump has limitations that the user must be aware of. The heat from the HVAC system is only the primary heat source in warmer climates where little or no heat is required. Colder climates still require a secondary heat source at floor level for optimum cabin comfort. Resistance Heat Power and Capacity Defrost Required Capacity Btu/Hr 60 F No 46,100 50F No 46, F No 46, F No 46, F No 46,100 Ambient Temp F How does the heat pump work and when is it most practical? Heat pumps in buses use the HVAC unit s electrically driven compressor in the existing refrigeration system to extract heat energy from the outdoor air and use that heat to warm the cabin. The size of the system and the ambient temperature determine how much heat can be made available. The use of heat pumps across all applications is most popular in moderate Heater Power Fan Power Total Input- Power Heat Pump Power and Capacity Defrost Required Capacity Btu/Hr Compressor Power Fan Power Total Input Power 60 F No 120, F No 105, F Yes 87, F Yes 68, climates, where the ambient temperature does not drop too far below freezing. The charts show typical ambient conditions and the heat capacity to expect from the heat pump and electric resistance heat. This comparison shows the power requirements and capacities at several ambient temperatures for both configurations. One key takeaway is that the resistance heat requires the same power and constant capacity in all ambient conditions, but power is drawn from the battery and no defrost is required. 20 F Yes 55, The other key takeaway is that while the heat pump provides more capacity for the ambient temperature down to the lower operating limit, power is still drawn from the battery to operate the compressors and fans. Thermo King Corporation 3

4 Ambient Temp F Effect of Defrost on Power and Capacity % Time in Defrost Capacity Btu/ Hr Compressor Power Fan Power Total Input Power 40 F 30% 61, F 30% 47, F 30% 38, F 20% 70, F 20% 54, F 20% 44, F 10% 78, Another factor to consider is defrost, which is required in lower ambient temperatures (typically beginning at 40 degrees F). How much time the system spends in the defrost mode can vary widely based on the ambient conditions. This chart shows three different scenarios in three different ambient temperatures. Note the loss of capacity while the system is in defrost. However, power is still being drawn from the battery. 30F 10% 61, F 10% 49, HEAT PUMPS: DESIGN, COST AND SERVICE DESIGN To add a heat pump to an existing system requires additional components and tubing COST The unit will be more expensive and, depending on the climate, resistance heat will still be required SERVICE The condenser becomes the evaporator in heat pump mode More components to service and diagnose when a failure occurs The condenser fans and compressors operate in winter, meaning additional run time with the compressor subjected to severe operating conditions, which leads to higher life cycle costs The condenser coil has to be tube and fin and will also be subjected to severe operating conditions with the freezing and thawing The weight and performance advantages of microchannel coil will be forfeited during air conditioning operation CONCLUSION: The application of heat pump technology for all-electric HVAC systems is feasible The power required to operate the heat pump versus resistance heat is not significantly different, but the heat pump delivers more output for the same input under similar operating conditions, making it more efficient The greater capacity provided by the heat pump should lead to less power being consumed when used alone within the specified operating range. The user must understand the limitations, costs and trade-offs Additional study and analysis is needed on several fleet operating profiles to understand the effect of heat pump usage on power consumption 4 Get Comfortable

5 ZERO EMISSION BUSES, ALL-ELECTRIC HVAC SPECIFICATIONS AND PASSENGER COMFORT The subject line looks busy and is clearly about three different things. However, the three are related in ways that you might not expect. This conversation is intended to start a discussion between the stakeholders; the suppliers, the operators and the most important stakeholder, the passenger. To frame this conversation properly, and to establish the context for the rest of the article, let s start with the passenger and work our way back. I can assure you that it will all come together. The Passenger: The most important thing that an operator can do to get people to ride the bus, who otherwise might not use the bus, is to create a comfortable environment. Just ask any operator what they fear most and you are likely to hear among other things, cold bus complaints in the winter and hot bus complaints in the summer. So, throughout all of the years of advancements in vehicle and component efficiency, none have been made at the expense of passenger comfort. In fact, passenger comfort either drove, or received benefit from most efficiency improvements. One would have to believe that the improvements have contributed to the steady increase in ridership, especially in the high end markets. Zero Emission Buses: This is what I wrote in the last installment of this series. It s clear that the drive to zero emission in transit vehicles has started. So, what does this have to do with the HVAC? A lot, actually. The zero emission bus is powered by batteries and all of the electrical loads, like the all-electric HVAC, use power from the battery. As on conventional buses, the HVAC is the largest single load on the engine. Now, the load is on the battery and affects how far the bus can go on a single charge. I think that you can easily understand that reducing the load allows the bus range to improve. Operators have determined that they need a range of miles to ensure that routes can be completed on a single charge. In the effort to extend range various proposals have come forth for reducing the HVAC load. By far, the most popular proposal is to reduce and or limit the amount of cooling. One strategy proposed is to shut the HVAC off when the bus needs power to climb a hill or to conserve the power to allow the bus to finish the route. Another approach is to only cool the bus to degrees F rather than the commonly applied degrees F. It has also been suggested that a temperature delta be used based on the outside ambient temperature. If the temperature delta is set at 15 degrees to control the cooling demand, it means that the bus interior would only cool to 85 degrees F on a 100 degree F day. While all of these approaches seem plausible, and some have been applied in various markets, you would have to agree that some of these approaches will not be welcomed in certain areas of the US. Imagine getting on a bus on a 110 degree day in Phoenix and the interior is only 95 degrees F. All-Electric HVAC Specifications: This is an area that highlights the conflicting interests. Operators are now writing specifications for their all-electric buses, and guess what, they have the same HVAC cooling requirements as were used for conventional diesel and CNG driven buses. While it is true that the specifications should not be the same because the all-electric system provides constant cooling capacity rather than variable capacity based on engine speed, it doesn t look like operators are ready to give up the cooling they have become accustomed to. Based on the specifications, we continue to build systems with excess capacity that will never get used, and with excess power that must be managed. Summary: With these conflicting objectives, misaligned expectations and the absence of an effective communication forum, we are likely to hit a wall somewhere along the way. Success is dependent on all of the stakeholders working together. Each may have to give up something to achieve the end goal which is a highly efficient package that does not sacrifice passenger comfort. If we don t, people may abandon the bus. Thermo King Corporation 5

6 COMING SOON: SCREW COMPRESSOR FOR COACH APPLICATIONS The screw compressor has been widely used in Transit for 18 years, with upwards of 14,000 still in service. This exclusive technology has a compelling value proposition, which includes reliable, efficient operation, long life, low maintenance, and fuel savings with its two stages of unloading. Thermo King, along with Greater Richmond Transit Company (GRTC), one of our trusted Transit partners, has successfully completed two cooling seasons using the S616 Screw Compressor in a Coach application. The Coach has operated on a dedicated 300-mile round trip route daily during the summer months, with a mix of highway and stop-and-go duty since May The operator reported a 7% improvement in fuel economy compared to the current configuration with no cooling complaints and no out-of-service issues. Retro-fit kits will be available for certain Coach models by the 4th quarter of 2018, and testing will continue. For more information, please call Thermo King at Get Comfortable

7 NOW AVAILABLE! SOLAR FOR TRANSIT, COACH, AND SCHOOL BUSES. THERMOLITE SOLAR PANELS FROM THERMO KING: THE PERFECT SOLUTION FOR BATTERY MAINTENANCE Battery maintenance has been a serious issue for truck and bus companies for many years. Finally, a solution has come by utilizing a technology that has also been around for many years: solar energy. Perhaps the most common problem is getting buses started for work week routes after sitting all weekend. This situation has become even more problematic in recent years, with the introduction of new systems that draw power even when the bus is not operating. Solar power has been shown to be effective, with over 16,000 panels installed, including proven results on 40-foot and 60-foot Transit buses\ as well as Coach bus applications. THERMOLITE BENEFITS INCLUDE: Greatly extended battery life and prevention of costly road calls High-efficiency solar cells use latest technology to produce Abundant power, even in low light conditions - Designed for quick, easy installation in all applications - Prevents the need for costly super capacitors by ensuring that the system batteries have sufficient starting power Weatherproof panel construction for extreme durability and long system life year anticipated product life - 5 year warranty All of these benefits translate into extended battery life, better asset utilization and maintenance savings. For more information contact your Regional Bus Manager or your local Thermo King Dealer. Visit us at COACH SCHOOL TRANSIT Thermo King Corporation 7

8 PM TIP ALL-ELECTRIC HVAC MAINTENANCE BEST PRACTICES Meet Anthony Cohen, also known as Tony. In March 2017, Tony became the Executive Director/Vice President of Maintenance and Infrastructure for Long Beach Transit. Previously, Tony had served as head of maintenance for Gardena Bus Lines (GTrans) and Deputy Chief Operating Officer at Sunline Transit. Gardena Bus Line had a fleet of 57 hybrid electric buses, all equipped with all-electric HVAC, giving them the distinction of being the largest (and perhaps only) 100% all-electric HVAC fleet in Transit. Tony and Gardena Bus Line were also distinguished in 2012 by being the recipients of the Thermo King Energy Efficiency Award for the agency s commitment to Energy Efficiency and Sustainability. I visit with Tony every year and hear first-hand about the challenges he sees with preventative maintenance. Tony was committed to making sure his fleet delivered on the value proposition that came with all-electric HVAC. One of the allelectric value propositions for Tony s units with dual scroll compressors was that one compressor would shut down when the cabin reached set point and typically stay off for the rest of the day. A California winter brings warm days where HVAC is needed, but one compressor could handle the cooling. All was well until the hot temperatures came suddenly and unexpectedly one year, and the units had to perform at maximum capacity. Tony was forced to pull units out of service for HVAC issues. To solve the problem, Tony developed a preventative maintenance schedule that ensured each unit was thoroughly checked before the warm weather set in. The results were impressive. In a subsequent visit, he informed me that he went the entire summer with zero HVAC failures. To add to the feat, it was the summer of 2015, which was exceedingly hot all across the country. Can you imagine having 100% utilization of a critical asset? If you own units with all-electric HVAC, please follow the recommended preventative maintenance schedule for best results. In addition to the 6,000 mile checks, Thermo King recommends an annual pre-season checkout prior to the beginning of the cooling season. For the detailed procedures, please refer to Service Bulletin SB Pre-Season Maintenance Inspection for All-Electric HVAC Systems Ingersoll Rand, plc. A publication for the mobile climate control industry MS Managing Editor/Writer: Michael O Brien Contributing Editor: Steve Johnson Layout and Design: Todd Gillenwaters For more information, contact Michael O Brien at or michael_obrien@thermoking.com Thermo King Corporation 314 West 90th Street, Minneapolis, MN